American consumers have long been skeptical about weight-loss supplements, and rightly so. With dozens of nutrients, herbs, and food extracts being marketed as aids for weight loss, there is shockingly little reliable information available concerning the safety and efficacy of any given product. What is more, many so-called miracle pills and quick fixes fail to deliver on the grand weight-loss promises they make, others come with unpleasant side effects, and some have even proven to be dangerous when used incorrectly.

According to Georgetown medical professor Harry Preuss, MD, MACN, CNS, however, there are a number of non-drug weight-loss aids available that do work and can help people shed pounds, build muscle, and burn fat. Based on his own research as well as hundreds of previously recorded scientific studies conducted at major universities and published in leading medical journals, in Dr. Preuss’s new book new book with Bill Gottlieb, THE NATURAL FAT-LOSS PHARMACY (Broadway Books, January 2007), he helps consumers separate the good from the bad and the helpful from the hype and lists the safe, effective, and natural weight-loss supplements on the market.

* HCA (hydroxycitric acid): An extract from the rind of the tamarind fruit, HCA interferes with an enzyme that triggers the formation of fatty acids, cholesterol and triglycerides. It helps lower blood levels of leptin (the substance that triggers hunger), increases serotonin and fat oxidation, and increases production of glycogen, leading to a filling of “fullness.” Study participants taking HCA ate up to 30% less food at every meal.

* MCT (medium chain triglycerides): This class of fatty saturated acids found naturally in coconut and butter help the body burn more calories – up to 25-30% more. The supplement leads to a drop in LDL (bad) cholesterol and reduction in body fat.

* Green and oolong tea extract: One of the antioxidants in green tea is EGCG, which beside possibly preventing cancer, high blood pressure, and diabetes, can also cut down on the creation of body fat and help destroy it through increased oxidation. Studies show that supplements containing EGCG increase calorie-burning by up to 180 calories a day.

* CLA (conjugated linolenic acid): In a study reported in the June 2004 issue of the American Journal of Clinical Nutrition, 180 healthy, overweight men and women were given either CLA or a placebo for one year. On average the CLA group lost 5 pounds of fat and gained 2 pounds of firming muscle – without diet or exercise.

* Chromium: Twenty-five years of research shows that taking supplements of this “trace mineral” can improve the insulin system, which regulates blood sugar levels. With enough chromium, muscle cells can make muscle, there’s less extra sugar to be stored as fat, and excess fat can be burned as fuel. In a study, women who took chromium lost 84% of their weight as fat, while women not taking the supplements lost 92% of their weight as muscle.

* Starch blockers (bean, wheat, hibiscus) and sugar blocker (L-arabinose): Many scientists now agree that cutting down on refined carbohydrates can not only help you get and stay trim, but also help you avoid diabetes, stroke, heart disease, and cancer. It may even slow the aging process. But low-carbohydrate diets are only one option. A smart alternative: carb-blockers made from a bean or wheat or hibiscus flower extract, which block the absorption of refined carbs in the digestive tract if taken before or during a high-carb meal, like pasta or pizza. L-arabinose, a simple sugar found in foods like corn, works to block the absorption of sucrose, meaning you can have your cake and lose the carbohydratess and calories.

* Chitosan and other soluble fibers: In an effort to clean up oil spills, scientists discovered chitosan, a pulverized powder made from the shells of shrimp and crab. This ultra-absorbent powder soaks up oil, grease, and heavy metals, both in the oceans and in the intestinal track. In 1995 Italian researchers gave either chitosan or a placebo to 150 people, who were on a 1,000-calorie-a-day diet for 4 weeks. Those on the placebo lost 4% of their weight, while those on chitosan lost 13%. Other studies show that chitosan can lower cholesterol by 29%. Psyllium, pectin, and guar gum are other soluble fibers that work similarly.

* 5-HTP (5-Hydroxyl-L-tryptophan): Due to high-stress, many people in America have low levels of serotonin, a brain chemical that controls appetite and mood. The result: overeating. 5-HTP is a natural amino acid that boosts serotonin, helping decrease food cravings and also creating a calm state of mind that is less vulnerable to emotional overeating. In an Italian study, overweight women who took serotonin spontaneously began to cut their calories – by more than 1000 calories per day.

* Cacti (Hoodia and Caralluma): The bushmen of the Kalahari desert rely on Hoodia, a form of cactus, to relieve hunger and thirst pangs. Caralluma is an edible Indian cactus that is used in chutneys and pickles and to control appetite, particularly in times of famine. As with Hoodia, scientists speculate that unique molecules in Caralluma affect the hypothalamus, switching off appetite. It can also normalize blood sugar, and after thousands of years of use, there are no known side effects.

* HMB (Hydroxy methylbutyrate): HMB is a metabolite, or a breakdown product of leucine, a component of protein that aids muscle-building. Although found in foods like alfalfa sprouts and catfish, only a supplement can provide enough to protect and build muscle. You do have to exercise to get the benefit of this supplement, but it is especially helpful to those 70 or older as well as AIDS and cancer patients and can lower blood pressure and high cholesterol.